US3255300A - Electric furnace cable - Google Patents

Description

June 7, 1966 s. BUNIsH ETAL 3,255,300

ELECTRIC FURNACE CABLE Filed D90. 19, 1963 FIG. 1

ATTORNEYS United States Patent O 3,255,300 ELECTRIC FURNACE CABLE Stephen Bunish and Olav E. Jore, Marion, Ind., assignors to Anaconda Wire and Cable Company, a corporation of Delaware Filed Dec. 19, 1963, Ser. No. 331,773 4 Claims. (Cl. 174-130) This invention relates to electric cables which are formed with a plurality of helically wound strands of wire, and it particularly relates to such a cable having a plurality of layers of low electrical resistance wires defining each of the strands with the diameter of the wires dening the outer layer of the strands being substantially larger than the diameter of the wires defining the inner layers of the strands. It also relates to electric-furnace assemblies using electric-furnace cables formed in this manner,

Electric caibles, such as those that are used with electric furnaces, are usually constructed from a plurality of helically wound strands of Wire, each strand of which is forme-d of helically wound layers of low electrical resistance wires. In use, a plurality of these cables are grouped together leading to a single electrode of the furnace. Being so closely grouped together, the magnetic elds which surround the cables set up forces which cause the cables constantly and violently to bang together and slide relative to each other thereby subjecting the individual strands of the cables to severe structural injury as a result of the impact forces between the individual strands within the group as well as the strands of other groups adjacently located, and to chafing against the other cables in the group. It can particularly be appreciated that with electric-furnace cables which are used as lead wires to the electrodes in an arc furnace through which cur-rent surges periodically, a magnetic eld is set up around thegcables which varies to extremes of intensity and causes great relative movement between adjacent cables. As would be expected, the greatest physical damage is done to the individual wires along the outer layer of the strands comprising the cable, and although the damage which is done to these wires is in the nature of physical damage, the cables do not suffer from mechanical but rather from electrical failure which is caused by a break in one or several of the individual wires in the outer layer.

We have found that an electric cable can be constructed which retains similar flexibility as cables heretofore constructed and has equal or better electrical conductivity and yet is able to withstand the physical abuse of impacting and chang in use, so as substantially to preclude electrical failure of the cables as result of the detrimental physical injury. Broadly stated, the electric cable of the invention is comprised of a plurality of strands of wire helically Wound to dene the cable and a plurality of layers of low electrical resistance wires :defining each of the strands. The strands are comprised of an outer layer of wires and in inner layer of wires with the diameter of the wires defining the outer layer of the strands Ibeing substantially larger than the diameter of the wires defin.

ing said inner layer of wires. It has particularly been found that the wires defining the outer layer of the strands should have a size from about #l2 AWG to about #9 AWG and the Wires defining the inner layers have a size Nice.

from about #16 AWG to about #14 AWG. It has also been found that in order effectively to prevent physical injury and the resultant electrical failure of the cables, the outer layer wires should comprise from about 55% to 65% of the total circular mil area of the cable and the inner layers of wires should comprise from about 35% to of the circular mil area of the cable. Cables as described above have particular application and offer decided improved results when used in combination with electric furnaces in which a plurality of electric-furnace cables formed according to `the invention are grouped closely together and connected to the furnace.

By low electrical resistance wires in this application, it is intended to include copper and aluminum wires or their conducting alloys and it is not intended to include steel wires which have poor electrical conductivity properties although perhaps have greater mechanical strength and would be less susceptible to .physical injury. Steel wires would have no application as conductors even though they would be highly resistant to impact and chaling damage.

A preferred embodiment of the invention is described Ahereinbelow in reference to the drawing wherein:

FIG. l is a perspective of a typical installation of electric-furnace cables showing them connected to the electrodes of the furnace and to its power source;

FIG. 2 is a longitudinal side elevation partly broken away to show the layers of strands in wires; and

FIG. 3 is an enlarged section partly broken away showing the construction of the cable of the invention.

As shown in FIG. 1 a plurality of electric-furnace cables 10 are grouped in a common installation for an electric arc furnace 11. Three electrodes 12 extend into the furnace 11 from a top portion thereof and attached to each of the electrodes and extending laterally outwardly beyond the electric furnace are connection bars 13. Electrically connected to each of the connecting bars 13 are one to forty cables per .phase depending upon the size of the furnace 10 which are maintained grouped together by wooden rings 1'4 or some other spacers which Y are shown positioned near the respective ends of the groups of cables and at the middle of the group. The groups of electric cables lead from the connecting bars 13 to a suitable power source 15.

Referring now to FIGS. 2 and 3, the particular construction of the electric cable of the invention is shown. The electric cable 10 is formed of a central strand 16 and six outer strands 17 which are helically Wound about the center strand 16 in a substantially long-lay pitch. Each of the strands comprising the cables are identically constructed. Thus, reference will be made below to the construction of a single strand as it is intended that each -of the strands in the cable is identically constructed. Referring to FIG. 3 the strand consists of a plurality of wires which are helically wound, also in a long-lay pitch, to form an elongated strand. The wires are constructed of copper or aluminum or their conducting alloys depending upon whether the maximum in conductivity or the minimum in weight is desired. A straight elongated center wire 18 is located within the center of the strand and extends longitudinally throughout the entire length thereof. Immediately surrounding the center wire 18 and helically wound thereabout in a relatively long-lay pitch are six wires 19 of an identical size as the center wire 18. Wound Vthat by providing an electric cable of the type described,

no appreciable diminishing of flexibility was found and the electric failure of thesecables as result of this irnpacting and chafing was greatly reduced. Although it siderable impact damage as a result of banging against each other and are particularly subjected to chafing between the closely grouped cables as they rub together by moving longitudinally relative to each other and also ing wires 19. Helically wound about the layer of twelve 5 iS beleVed that the Pafllcllafdconstructlfm,gieitecg wires 20 and helically oriented in a direction opposite Cable Per Se Offers deelde a Ventagesl 1I1 I S f into the direction of the twelve wires 20 and in the same l?Ortanlc tno note that the assmbiy ,of e ecmc um'fis 1 direction as the six helically wound wires 19 is an outer 3011301 ating cames of the iiiveiiiioii Offers partlular y layer 21 of Wires having a diameter greater than the di decided advantages over assemblies of this type eretoameter of the inner layers of wires 18, 19, and 20. The misliiligg. 'ouler layer 0f- Wlres 21 1S consiructed of the Same ma* 1. An electric furnace cable for use with other similar termi as .the Inner layers Gf Wires and the my of the cables as leads to an electric furnace, said cable being re- Ouier iayer is generally lefthanded eind opposite to the sistant to physical damage along its outer layer iof strands iayei.' beneath iii but occasionally rlghthandeday or 15 comprising a plurality of strands of wire helically wound iieii'iiigboiie iay is used Although a Strand hai-Img two to define the cable, and a plurality of layers of low elec- Inner layers has 'been described 1t lslof Fourse mtendiid trical resistance wires defining each of said strands, said that there can be for example one to four inner layers as is Strands comprised of an Outer layer of Wires and inner conventional.

la ers of wires with the diameter of the wires defining It has been fouiid thai there is a definiti? size limitation this outer layer of the strands being substantially larger between me ieiaiivei diameters .of the .inner layers (if than the diameter of the wires defining said inner layers wires and the outer layers of wires which provides the of wire optimum iii iiexibiiity and Sti-engin t0 resist imm. and 2. An electric furnace cable for use with other similar c.ha.ng damage' Cables having Wires failing .outside the cables as leads to an electric furnace, said cable being re- `iimiis .specified have belen. .found .to be inferior m that 25 sistant to physical damage along its outer layer of strands they either lack the iiexibiiiiy (.iesired or do not provide comprising a plurality of strands of wire helically wound sigriicant protection to ihe iniurious physical .forces to to define the cable, and a plurality of layers of low elec- Wiiicii the Cabies are subiected' The larger Wires coin' trical resistance wires defining each of said strands, said prisiiig the Outer iayer of each strand Should have .a Size strands comprised of an outer layer of wires and inner from abiui #12 AWG to abo. #9 AWG and their cir' 30 layers of wires with the diameter of the wires defining the Cuiar mii area Shouid comprise approximately 60.%. of outer layer of the strands being of a size from about #12 the circular mil area olf1 the complteilidcilble. The siiiilar AWG to about #9 AWG and the diameter of the Wires core of wires of eac strand s ou ave a size rom 16 about #i6 AWG to about #i4 AWG and their total fviinsfemg of a me from about ii circuiai mii ama Wiii comprise appioximaieiy 40% of 35 3. An electric furnace cable for use with other similar me irciiiar mii area 0f, the compieied ,cabiii ,In Prac' cables as leads to an electric' furnace, said cable being reiice it has bien foiiiid this 60`40% ieiaiifiiisiiip is the op sistant to physical damage along its outer layer of strands timum relationship between cables having larger wires comprising a plurality of Strands of Wire helically Wound miimg Wiiiim me range of 65% of me ciiciiiar mii to define the cable and a plurality of layers of low elecam? of me compieied cabie 'and Smaiiei Wii-is faiimg 40 trical resistance wires dening each of said strands, said Wimm me range of 35`4 5% of the Ciiciiiai mii area of strands comprised of an outer layer of wires and inner me compieied 'cabie which is kiiowii i0 provide Work' layers of wires with the diameter of the wires defining the able Cables Set forth below lnthe table are a list 0f outer layer of the strands being substantially larger than the more popular sizes of an electric-furnace cable showthe diameter 0f the Wil-es defining Said inner layers of Ilg the Preferred relationship ln SlZeS and numbers 0f 45 wires so that the total circular mil area of said outer wires. layer wires will comprise from about 55 to 65% of the Final Total No. Number No. of No.01' Nominal Area of Cross O.D.of of Wires in of Wires No. of Inner Outer Sec. Cir. Mils. Cable Cable in Each Strands Wires Wires Strand and Size and Size 2,000,000-- 1.83 357 51 7 37/.0556 14/. 1110 1,s26,000 1.77 350 50 7 37/.0531 13/.1097 5o, 1. 74 350 5o 7 37/. 0520 13/.1075 1,500,000-- 1. 6i 350 50 7 37/.0481 13/. 0905 1,250,000 1. 47 224 32 7 10/.0613 13/ 0908 1,000,000 1. 3i 224 32 7 19/. 0548 13/.0812

Referring now to FIG. 1 it can be seen that by grollptotal circular mil area of the cable and the diameter of ing a number of cables closely together and locating them the wires defining said inner layer wires will comprise adjacent to two other groups of cables having a similar about 35 to 45% of the total circular mil area of the number of cables, and particularly when the electric cable. furnace is an arc furnace wherein periodical arcing 4. An electric furnace cable for use with other similar causes great variance in the magnetic fields which are cables as leads to an electric furnace, said cable being reset up around each of the cables and around each of the sistant to physical damage along its outer layer of strands groups of the cables, this causes violentand rapid shakcomprising a plurality of strands of wire helically wound ing and banging of the cables against the cables of the to define the cable and a plurality of layers of low elecother group. For this reason the Wooden rings 14 or trical resistance Wires defining each of said strands, said spacers are provided to prevent shorting out between strands comprised of an outer layer of wires and inner phases between the cables ofthe respective groups. Such layers of Wires with the diameter of the wires defining prohibitive measures have not been effective, however. said outer layer of said strands being of a size from The cables within each group are also subjected to conabout #12 AWG to about #9 AWG and the wires defining said inner layers each having a size from about #16 AWG to about #14 AWG so that the total circular mil area of said outer layer of wires will comprise from about 55 to 65% of the total circular mil area of the damage by chafing against the spacers. It has been found cables and the diameter of the wires definingv said inner mil area of the cable.

References Cited by the Examiner UNITED STATES PATENTS 3,078,325 2/1963 Dillon et al 12-9 OTHER REFERENCES Federal Specification, Wire Rope and Strand, RR-W- 5 410g, April 19, 1960, p. 51, FIG. 39.

Jenkin 57--148 ROBERT K. SCHAEFER7 Primary Examiner.

Grimes et al. 57-145 l0 D. A. KETTLESTRINGS, Assistant Examiner.

Claims (1)

1. AN ELECTRIC FURNACE CABLE FOR USE WITH ONE SIMILAR CABLES AS LEADS TO AN ELECTRICAL FURNACE, SAID CABLE BEING RESISTANT TO PHYSICAL DAMAGE ALONG ITS OUTER LAYER OF STRANDS COMPRISING A PLURALITY OF STRANDS OF WIRE HELICALLY WOUND TO DEFINE THE CABLE, AND A PLURALITY OF LAYERS OF LOW ELECTRICAL RESISTANCE WIRES DEFINING EACH OF SAID STRANDS, SAID STRANDS COMPRISED OF AN OUTER LAYER OF WIRES AND INNER

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